[Coral-List] Excess algal symbionts increase coral susceptibility to bleaching

Douglas Fenner douglasfennertassi at gmail.com
Mon Nov 19 18:55:51 EST 2012

*The spatial pattern of bleaching does not correspond well with the pattern
of dust.
*African dust fell in the Caribbean long before reefs there started to

Although the Caribbean receives significant inputs of African Dust, the
Pacific does not.  There was significant bleaching in the Pacific in 1998
in several places, I know that Palau was hit fairly hard.  The worst
bleaching in 1998 was in the Indian Ocean.  The northern Indian Ocean does
get desert dust at times, as shown in the map that Gene pointed to (a
fabulous map which someone else told me about and I passed on).  But the
map does not show dust over most of the Indian Ocean, and there was massive
bleaching south of the dust area.  Thus, the pattern of bleaching in 1998
does not closely match that of the dust.  The main caveat to that is that I
don't know when the data for the map was taken.  It looks to me like a
snapshot, since it shows individual storms.  But I don't know when it was
based on, and with time these things can change greatly (though the pattern
is likely to change relatively little).  The main desert areas are north of
the Indian Ocean, so it doesn't make sense that the middle and southern
Indian Ocean would get dust.  But the Pacific Ocean can have bleaching in
spite of very little dust.  Here in American Samoa, the NOAA weather
station on the windward side of the island measures some of the purest air
anywhere on earth, since there are many thousands of miles of ocean in all
directions, particularly east of us where the air usually comes from.  And
yet bleaching events have occurred here.  Mass bleaching corresponds most
closely with temperatures, and bleaching events can be predicted quite well
based on temperatures alone, including in areas without any dust.  Other
variables can have effects as well, for example the first mass bleaching
event reported was from fresh water, if I remember (in Jamaica reported by
Tom Goreau senior).
     Isn't it the case that African dust has been falling in the Caribbean
for a very long time, at least 10's of thousands of years?   I believe
there are layers of it in places like the Bahamas that are very old,
deposited long before the current decline of the coral reefs began.
    Cheers,  Doug

On Fri, Nov 16, 2012 at 11:34 AM, Eugene Shinn <eshinn at marine.usf.edu>wrote:

> Andrew, This is very interesting information especially because
> you're findings relate the combined effects of temperature, oxygen,
> and nutrients to bleaching.  We certainly have all three, including
> anthropogenic nutrient sources, in Florida but I keep remembering the
> sudden die-off of Acroporids at San Salvador in 1983. That was a time
> when there were few anthropogenic sources on that sparsely populated
> island surrounded by deep oceanic water. John Martins original
> discovery that iron was necessary for algal growth has been re
> confirmed by many experiments since then. Because 1983 and 1984 were
> peak years for African dust flux to the Caribbean I continue to
> wonder if it contained sufficient iron (also phosphate) to provide
> this necessary micro nutrient? It is certainly the source of the red
> soil on that otherwise limestone island. Could the 5-6 percent iron
> contained in African dust be sufficient to cause overstimulation of
> both cyanobacteria and dynoflagelate zooxanthellae and thus cause
> their expulsion i.e. bleaching?
>        Considering the co incidence of bleaching events with years of
> increased dust flux and warm quiescent summers makes one wonder. The
> year 1998 was especially warm and dust flux as measured at Barbados
> by Joe Prospero was almost as high as it was in 1983 and 1984. With
> such obvious correlations one would think that some curious coral
> biologist would have performed dosing experiments to validate or
> discard the dust hypothesis. Gene  PS: here is a great image of the
> dust belt provided by Douglas Fenner.
> <http://www.nasa.gov/multimedia/imagegallery/image_feature_2393.html>
> --
> No Rocks, No Water, No Ecosystem (EAS)
> ------------------------------------ -----------------------------------
> E. A. Shinn, Courtesy Professor
> University of South Florida
> College of Marine Science Room 221A
> 140 Seventh Avenue South
> St. Petersburg, FL 33701
> <eshinn at marine.usf.edu>
> Tel 727 553-1158----------------------------------
> -----------------------------------
> _______________________________________________
> Coral-List mailing list
> Coral-List at coral.aoml.noaa.gov
> http://coral.aoml.noaa.gov/mailman/listinfo/coral-list

Dept. Marine & Wildlife Resources, American Samoan Government
PO Box 7390
Pago Pago, American Samoa 96799  USA

More information about the Coral-List mailing list